Conjugated polymers from substituted 3,4-propylenedioxythiophene, compositions, method of making, and use thereof

ABSTRACT

Polymers and copolymers having units derived from substituted 3,4-propylenedioxythiophene are disclosed. Also provided are methods of making and using the same.

CROSS REFERENCE TO RELATED APPLICATION

This is a divisional application of application Ser. No. 12/356,594 filed Jan. 21, 2009 which claims the benefit of U.S. Provisional Application Ser. No. 61/022,400 filed Jan. 21, 2008, each of which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

This invention relates to conjugated polymers prepared from unconventionally substituted 3,4-propylenedioxythiophene, compositions, method of producing such conjugated polymers, and applications utilizing the conjugated polymers.

BACKGROUND

Polymers based on alkylenedioxythiophene are materials used in electrochromics as many have the ability to change color from blue to colorless. Another advantage is that some alkylenedioxythiophene monomers can be prepared in one step from commercially available 3,4-dimethoxythiophene. 3,4-Ethylenedioxythiophene (EDOT) polymerizes oxidatively to produce polyEDOT having the ability to transition from deep blue to sky blue upon oxidation with a photopic contrast of approximately fifty percent. Higher photopic contrast and a more colorless bleached state is obtained by incorporation of an additional methylene unit into the EDOT repeat unit with 3,4-propylenedioxythiophene (PropOT).

Known conjugated polymers do not transition from a green to a colorless state, although some are known to transition through a green color.

There remains a continuing need in the art for new materials having electrochemical properties not yet achieved in known materials.

BRIEF SUMMARY OF THE INVENTION

In one embodiment, a polymer comprises a unit derived from a substituted 3,4-propylenedioxythiophene monomer according to the structure (I):

wherein each instance of R¹, R², R³, and R⁴ independently is hydrogen; optionally substituted C₁-C₂₀ alkyl, C₁-C₂₀ haloalkyl, aryl, C₁-C₂₀ alkoxy, C₁-C₂₀ haloalkoxy, aryloxy, —C₁-C₁₀ alkyl-O—C₁-C₁₀ alkyl, —C₁-C₁₀ alkyl-O— aryl, —C₁-C₁₀ alkyl-aryl; or hydroxyl; with the proviso that at least one of a R¹ or a R² group is not hydrogen; wherein the C₁-C₂₀ alkyl, C₁-C₂₀ haloalkyl, aryl, C₁-C₂₀ alkoxy, C₁-C₂₀ haloalkoxy, aryloxy, —C₁-C₁₀ alkyl-O—C₁-C₁₀ alkyl, —C₁-C₁₀ alkyl-O-aryl, or —C₁-C₁₀ alkyl-aryl group each may be optionally substituted with one or more of C₁-C₂₀ alkyl; aryl; halogen; hydroxyl; —N—(R⁷)₂ wherein each R⁷ is independently hydrogen or C₁-C₆ alkyl; cyano; nitro; —COOH; —S(═O)C₀-C₁₀ alkyl; or —S(═O)₂C₀-C₁₀ alkyl.

In another embodiment, a method comprises polymerizing a composition by electrochemical or chemical reaction to form a polymer, wherein the composition comprises substituted 3,4-propylenedioxythiophene monomer according to the structure (I):

wherein each instance of R¹, R², R³, and R⁴ independently is hydrogen; optionally substituted C₁-C₂₀ alkyl, C₁-C₂₀ haloalkyl, aryl, C₁-C₂₀ alkoxy, C₁-C₂₀ haloalkoxy, aryloxy, —C₁-C₁₀ alkyl-O—C₁-C₁₀ alkyl, —C₁-C₁₀ alkyl-O— aryl, —C₁-C₁₀ alkyl-aryl; or hydroxyl; with the proviso that at least one of a R¹ or a R² group is not hydrogen; wherein the C₁-C₂₀ alkyl, C₁-C₂₀ haloalkyl, aryl, C₁-C₂₀ alkoxy, C₁-C₂₀ haloalkoxy, aryloxy, —C₁-C₁₀ alkyl-O—C₁-C₁₀ alkyl, —C₁-C₁₀ alkyl-O-aryl, or —C₁-C₁₀ alkyl-aryl group each may be optionally substituted with one or more of C₁-C₂₀ alkyl; aryl; halogen; hydroxyl; —N—(R⁷)₂ wherein each R⁷ is independently hydrogen or C₁-C₆ alkyl; cyano; nitro; —COOH; —S(═O)C₀-C₁₀ alkyl; or —S(═O)₂C₀-C₁₀ alkyl.

In another embodiment, a substituted 3,4-propylenedioxythiophene according to the structure (I):

wherein each instance of R¹, R², R³, and R⁴ independently is hydrogen; optionally substituted C₁-C₂₀ alkyl, C₁-C₂₀ haloalkyl, aryl, C₁-C₂₀ alkoxy, C₁-C₂₀ haloalkoxy, aryloxy, —C₁-C₁₀ alkyl-O—C₁-C₁₀ alkyl, —C₁-C₁₀ alkyl-O— aryl, —C₁-C₁₀ alkyl-aryl; or hydroxyl; with the proviso that at least one of a R¹ or a R² group is not hydrogen; wherein the C₁-C₂₀ alkyl, C₁-C₂₀ haloalkyl, aryl, C₁-C₂₀ alkoxy, C₁-C₂₀ haloalkoxy, aryloxy, —C₁-C₁₀ alkyl-O—C₁-C₁₀ alkyl, —C₁-C₁₀ alkyl-O-aryl, or —C₁-C₁₀ alkyl-aryl group each may be optionally substituted with one or more of C₁-C₂₀ alkyl; aryl; halogen; hydroxyl; —N—(R⁷)₂ wherein each R⁷ is independently hydrogen or C₁-C₆ alkyl; cyano; nitro; —COOH; —S(═O)C₀-C₁₀ alkyl; or —S(═O)₂C₀-C₁₀ alkyl.

Other embodiments include methods of producing the substituted 3,4-propylenedioxythiophenes, the substituted PropOT polymers, and applications utilizing the substituted PropOT polymers.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates the results of cyclic voltammetry of a 10 mM aDM-PropOT/100 mM TBAPF₆ solution.

FIG. 2 illustrates the scan rate study of aDM-PropOT polymer film.

FIG. 3 illustrates the spectroelectrochemistry of aDM-PropOT in 0.1 V potential steps in acetonitrile and 0.1M TBAPF₆ on ITO glass.

DETAILED DESCRIPTION OF THE INVENTION

PropOT has three methylene units in its ring structure. Disclosed herein are substituted 3,4-propylenedioxythiophene monomers (“substituted PropOT monomers”) substituted alpha to the monomer oxygen(s), and optionally further substituted at the central methylene unit. Upon conjugation, the resulting electrochromic conjugated polymers (“substituted PropOT polymer”) exhibit different colors in the reduced state that are blue shifted from conventional polypropylenedioxythiophene (“polyPropOT”), which is a deep blue. Not wishing to be bound by theory, the blue shift is likely due to the steric interactions between the repeating units of the substituted PropOT polymer. The substituted PropOT polymers can have a green or red color in the reduced state depending upon the size of the substituent and the degree of interaction with the neighboring repeat units. As the steric interactions increase, the wavelength for maximum absorption (λ_(max)) of the substituted PropOT polymer in the reduced state blue shifts to higher energy.

The color of the substituted PropOT polymer in the oxidized state is optically transparent (colorless) similar to known unsubstituted polyPropOT in the oxidized state. The high optical transparency in the oxidized state is controlled by the conductivity of the polymer. Introduction of disorder into the structure is one method for decreasing interchain carrier mobility resulting in a decrease in the intensity of the optical transition occurring at the low energy of the near infrared region (NIR), one factor in obtaining a colorless oxidized state. By adding substitution alpha to the oxygen(s) of the 3,4-propylenedioxythiophene core will provide a disruption of conjugation of the polymer in order to increase the energy of the pi-pi* transition. The substitution will introduce steric interactions that would decrease interchain interactions of the polymer thereby increasing the optical transparency in the bleached state. Not wishing to be bound by theory, it is theorized the alpha substituents would project over the conjugated polymer backbone thereby causing steric interactions to distort thiophenes of the backbone out of planarity compared to unsubstituted 3,4-propylenedioxythiophene polymers and where the central carbon of PropOT is substituted with an alkyl group. The distortion of planarity will be proportional to the size of the substituent groups. Tetraethyl substituents are expected to further blue shift the λ_(max) with respect to the dimethyl substituents. As the substituent increases in size (e.g. increasing size of alkyl groups) it is anticipated that the polymer should transition to a highly transparent state in the semiconductive form. Longer alkyl substituents would further provide solubilization in organic solvents.

Other approaches besides the alpha substitution to change the color transition are discussed further herein.

The starting substituted PropOT monomers used to prepare the substituted PropOT polymers include those according to the general structure (I):

wherein each instance of R¹, R², R³, and R⁴ independently is hydrogen; optionally substituted C₁-C₂₀ alkyl, C₁-C₂₀ haloalkyl, aryl, C₁-C₂₀ alkoxy, C₁-C₂₀ haloalkoxy, aryloxy, —C₁-C₁₀ alkyl-O—C₁-C₁₀ alkyl, —C₁-C₁₀ alkyl-O— aryl, —C₁-C₁₀ alkyl-aryl; or hydroxyl; with the proviso that at least one of a R¹ or a R² group is not hydrogen. The C₁-C₂₀ alkyl, C₁-C₂₀ haloalkyl, aryl, C₁-C₂₀ alkoxy, C₁-C₂₀ haloalkoxy, aryloxy, —C₁-C₁₀ alkyl-O—C₁-C₁₀ alkyl, —C₁-C₁₀ alkyl-O-aryl, or —C₁-C₁₀ alkyl-aryl groups each may be optionally substituted with one or more of C₁-C₂₀ alkyl; aryl; halogen; hydroxyl; —N—(R⁷)₂ wherein each R⁷ is independently hydrogen or C₁-C₆ alkyl; cyano; nitro; —COOH; —S(═O)C₀-C₁₀ alkyl; or —S(═O)₂C₀-C₁₀ alkyl.

Specifically each instance of R¹ and R² independently is hydrogen; optionally substituted C₁-C₁₀ alkyl, C₁-C₁₀ haloalkyl, aryl, C₁-C₁₀ alkoxy, C₁-C₁₀ haloalkoxy, aryloxy, —C₁-C₅ alkyl-O—C₁-C₅ alkyl, —C₁-C₅ alkyl-O-aryl, —C₁-C₅ alkyl-aryl; or hydroxyl; and R³ and R⁴ are both hydrogen; with the proviso that at least one of a R¹ or a R² group is not hydrogen. The C₁-C₁₀ alkyl, C₁-C₁₀ haloalkyl, aryl, C₁-C₁₀ alkoxy, C₁-C₁₀ haloalkoxy, aryloxy, —C₁-C₅ alkyl-O—C₁-C₅ alkyl, —C₁-C₅ alkyl-O-aryl, or —C₁-C₅ alkyl-aryl groups each may be optionally substituted with one or more of C₁-C₂₀ alkyl; aryl; halogen; hydroxyl; —N—(R⁷)₂ wherein each R⁷ is independently hydrogen or C₁-C₆ alkyl; cyano; nitro; —COOH; —S(═O)C₀-C₁₀ alkyl; or —S(═O)₂C₀-C₁₀ alkyl.

More specifically each instance of R¹ and R² independently is hydrogen; optionally substituted C₁-C₅ alkyl, C₁-C₅ haloalkyl, aryl, C₁-C₅ alkoxy, C₁-C₅ haloalkoxy, aryloxy, —C₁-C₃ alkyl-O—C₁-C₃ alkyl, —C₁-C₃ alkyl-O-aryl, —C₁-C₃ alkyl-aryl; or hydroxyl; and R³ and R⁴ are both hydrogen; with the proviso that at least one of a R¹ or a R² group is not hydrogen. The C₁-C₅ alkyl, C₁-C₅ haloalkyl, aryl, C₁-C₅ alkoxy, C₁-C₅ haloalkoxy, aryloxy, —C₁-C₃ alkyl-O—C₁-C₃ alkyl, —C₁-C₃ alkyl-O-aryl, or —C₁-C₃ alkyl-aryl groups each may be optionally substituted with one or more of C₁-C₂₀ alkyl; aryl; halogen; hydroxyl; —N—(R⁷)₂ wherein each R⁷ is independently hydrogen or C₁-C₆ alkyl; cyano; nitro; —COOH; —S(═O)C₀-C₁₀ alkyl; or —S(═O)₂C₀-C₁₀ alkyl.

In one embodiment, at least two of the R¹ and R² groups are not hydrogen while the remaining two are hydrogen. Within this embodiment, both R¹ groups or R² groups are hydrogen while the remaining groups are other than hydrogen.

In one embodiment, each instance of R¹ and R² independently is hydrogen; or optionally substituted C₁-C₂₀ alkyl, C₁-C₂₀ haloalkyl, aryl, —C₁-C₁₀ alkyl-aryl; and R³ and R⁴ are both hydrogen; with the proviso that at least one of a R¹ or a R² group is not hydrogen. The C₁-C₂₀ alkyl, C₁-C₂₀ haloalkyl, aryl, —C₁-C₁₀ alkyl-aryl groups each may be optionally substituted with one or more of C₁-C₂₀ alkyl; aryl; halogen; hydroxyl; —N—(R⁷)₂ wherein each R⁷ is independently hydrogen or C₁-C₆ alkyl; cyano; nitro; —COOH; —S(═O)C₀-C₁₀ alkyl; or —S(═O)₂C₀-C₁₀ alkyl.

In another embodiment, each instance of R¹ and R² independently is hydrogen; or optionally substituted C₁-C₂₀ alkyl, C₁-C₂₀ haloalkyl, aryl, —C₁-C₁₀ alkyl-aryl; and R³ and R⁴ are both hydrogen; with the proviso that at least two of the R¹ or R² groups are not hydrogen. The C₁-C₂₀ alkyl, C₁-C₂₀ haloalkyl, aryl, —C₁-C₁₀ alkyl-aryl groups each may be optionally substituted with one or more of C₁-C₂₀ alkyl; aryl; halogen; hydroxyl; —N—(R⁷)₂ wherein each R⁷ is independently hydrogen or C₁-C₆ alkyl; cyano; nitro; —COOH; —S(═O)C₀-C₁₀ alkyl; or —S(═O)₂C₀-C₁₀ alkyl.

The starting substituted PropOT monomers to prepare the substituted PropOT polymers include those according to the general structure (II):

wherein the R¹ and R² are as described above.

In one embodiment, the substituted PropOT monomer meets the general structure (II) wherein each instance of R¹ independently is C₁-C₁₀ alkyl or benzyl and each instance of R² independently is hydrogen, C₁-C₁₀ alkyl, or benzyl. In another embodiment, the substituted PropOT monomer meets the general structure (II) wherein each instance of R¹ independently is C₁-C₅ alkyl or benzyl and each instance of R² independently is hydrogen, C₁-C₅ alkyl, or benzyl. In still yet another embodiment, the substituted PropOT monomer meets the general structure (II) wherein each instance of R¹ independently is C₁-C₃ alkyl or benzyl and each instance of R² independently is hydrogen, C₁-C₃ alkyl, or benzyl.

In one embodiment, the substituted PropOT monomers can be prepared via a trans-etherification reaction of 3,4-dialkoxythiophene with an appropriately substituted diol according to the general Scheme A below.

The starting 3,4-dialkoxythiophene can have a lower alkyl substituent for R⁵, specifically a C₁-C₄ alkyl, and more specifically a C₁-C₂ alkyl. Commercially available 3,4-dimethoxythiophene can be used.

The substituted diol according to general Scheme A contains groups R¹, R², R³, and R⁴ as defined above, or their appropriately protected functional group equivalents. Commercially available diols include 2,4-pentanediol, 2-methyl-2,4-pentanediol, 2,4-dimethyl-2,4-pentanediol, 3-methyl-2,4-heptanediol, and 7-ethyl-2-methyl-4,6-nonanediol, all of which are available from Sigma-Aldrich.

The reaction of the 3,4-dialkoxythiophene and diol is performed in the presence of a catalyst. Exemplary catalysts include sulfonic acids such as p-toluene sulfonic acid, dodecylbenzene sulfonic acid, and the like.

The solvent used in the reaction to prepare the substituted PropOT monomer can be any high boiling, inert organic solvent including an aromatic such as toluene, xylene, and the like; and a halogenated aromatic including ortho-dichlorobenzene; mixtures thereof; and the like.

The temperature of the reaction to prepare the substituted PropOT monomer can be at or about the boiling point of the solvent used. Specifically the reaction can be performed at temperatures of about 80 to about 300° C., more specifically about 90 to about 250° C., yet more specifically about 100 to about 200° C.

Also disclosed herein are conductive conjugated polymers that are obtained via conversion of a substituted PropOT monomer via chemical oxidation or electrochemical oxidation. These substituted PropOT polymers have utilities in a wide variety of applications, for example, electronic packaging, organic light-emitting diodes (LEDs), electrochromic windows and displays, optically transparent electrodes, volatile organic gas sensors, as well as other applications discussed herein.

The substituted PropOT monomers disclosed herein can be polymerized alone to form a conjugated homopolymer. Also provided herein are copolymers comprising units derived from two or more different substituted PropOT monomers. Also provided herein are copolymers comprising units derived from a substituted PropOT and an additional monomer (“co-monomer”) which provide a tailoring of the conductivity or optoelectronic properties of the resulting polymer. The co-monomer can include electroactive monomers or non-electroactive monomers. “Electroactive monomer” as used herein means a monomer or oligomer that is capable of copolymerization with substituted PropOT, and that imparts or enhances the electrical/electronic properties of the resulting copolymer, including such properties as electrical conductivity, semiconductivity, electroluminescence, electrochromicity, photovoltaic properties, or the like. “Non-electroactive monomer” means a monomer that is capable of copolymerization and that either decreases or does not adversely affect the electrical/electronic properties of the resulting copolymer.

Examples of suitable electroactive monomers include those known in the art to exhibit electroactivity, including but not limited to thiophene, substituted thiophene, thieno[3,4-b]thiophene, substituted thieno[3,4-b]thiophene, dithieno[3,4-b:3′,4′-d]thiophene, thieno[3,4-b]furan, substituted thieno[3,4-b]furan, bithiophene, substituted bithiophene, pyrrole, substituted pyrrole, phenylene, substituted phenylene, naphthalene, substituted naphthalene, biphenyl and terphenyl and their substituted versions, phenylene vinylene, substituted phenylene vinylene, and the like.

Suitable co-monomers include unsubstituted and 2- or 6-substituted thieno[3,4-b]thiophene and thieno[3,4-b]furan having the general structures (III), (IV), and (V):

wherein Q¹ is S or O; and R⁶ is hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl including perfluoroalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, or —C₁-C₆ alkyl-O-aryl. Specifically, Q¹ is S or O; and R⁶ is hydrogen.

3,4-Ethylenedioxythiophene, 3,4-ethyl ene dithiathiophene, 3,4-ethylenedioxypyrrole, 3,4-ethylenedithiapyrrole, 3,4-ethylenedioxyfuran, 3,4-ethylenedithiafuran, and derivatives having the general structure (VI):

wherein each occurrence of Q¹ is independently S or O; Q² is S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; and each occurrence of R⁶ is hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, or —C₁-C₆ alkyl-O-aryl.

Isathianaphthene, pyridothiophene, pyrizinothiophene, and derivatives having the general structure (VII):

wherein Q² is S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; each occurrence of Q³ is independently CH or N; and each occurrence of R⁶ is independently hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, or —C₁-C₆ alkyl-O-aryl.

Oxazole, thiazole, and derivatives having the general structure (VIII):

wherein Q¹ is S or O.

Pyrrole, furan, thiophene, and derivatives having the general structure (IX):

wherein Q² is S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; and each occurrence of R⁶ is independently hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, or —C₁-C₆ alkyl-O-aryl.

Bithiophene, bifuran, bipyrrole, and derivatives having the following general structure (X):

wherein each occurrence of Q² is independently S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; and each occurrence of R⁶ is independently hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, or —C₁-C₆ alkyl-O-aryl.

Terthiophene, terfuran, terpyrrole, and derivatives having the following general structure (XI):

wherein each occurrence of Q² is independently S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; and each occurrence of R⁶ is independently hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, or —C₁-C₆ alkyl-O-aryl.

Thienothiophene, thienofuran, thienopyrrole, furanylpyrrole, furanylfuran, pyrolylpyrrole, and derivatives having the following general structure (XII):

wherein each occurrence of Q² is independently S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; and each occurrence of R⁶ is independently hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, or —C₁-C₆ alkyl-O-aryl.

Dithienothiophene, difuranylthiophene, dipyrrolylthiophene, dithienofuran, dipyrrolylfuran, dipyrrolylpyrrole, and derivatives having the following general structure (XIII):

wherein each occurrence of Q² is independently S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; Q⁴ is C(R⁶)₂, S, O, or N—R⁷; and each occurrence of R⁶ is independently hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, or —C₁-C₆ alkyl-O-aryl.

Dithienylcyclopentenone, difuranylcyclopentenone, dipyrrolylcyclopentenone and derivatives having the following general structure (XIV):

wherein each occurrence of Q² is independently S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; and E is O or C(R⁸)₂, wherein each occurrence of R⁸ is an electron withdrawing group.

Other suitable heteroaryl monomers include those having the following general structure (XV):

wherein each occurrence of Q¹ is independently S or O; each occurrence of Q² is independently S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; each occurrence of R⁶ is independently hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, or —C₁-C₆ alkyl-O-aryl. In one embodiment, each occurrence of Q¹ is O; each occurrence of Q² is S; and each occurrence of R⁶ is hydrogen.

Dithienovinylene, difuranylvinylene, and dipyrrolylvinylene according to the structure (XVI):

wherein each occurrence of Q² is independently S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; each occurrence of R⁶ is independently hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, or —C₁-C₆ alkyl-O-aryl; and each occurrence of R⁹ is hydrogen, C₁-C₆ alkyl, or cyano.

1,2-Trans (3,4-ethylenedioxythienyl)vinylene, 1,2-trans(3,4-ethylenedioxyfuranyl)vinylene, 1,2-trans(3,4ethylenedioxypyrrolyl)vinylene, and derivatives according to the structure (XVII):

wherein each occurrence of Q³ is independently CH₂, S, or O; each occurrence of Q² is independently S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; each occurrence of R⁶ is independently hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, or —C₁-C₆ alkyl-O-aryl; and each occurrence of R⁹ is hydrogen, C₁-C₆ alkyl, or cyano.

The class bis-thienylarylenes, bis-furanylarylenes, bis-pyrrolylarylenes and derivatives according to the structure (XVIII):

wherein each occurrence of Q² is independently S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; each occurrence of R⁶ is independently hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, or —C₁-C₆ alkyl-O-aryl; and

represents an aryl. Exemplary aryl groups include furan, pyrrole, N-substituted pyrrole, phenyl, biphenyl, thiophene, fluorene, 9-alkyl-9H-carbazole, and the like.

The class of bis(3,4-ethylenedioxythienyl)arylenes, related compounds, and derivatives according to the structure (XIX):

wherein each occurrence of Q¹ is independently S or O; each occurrence of Q² is independently S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; each occurrence of R⁶ is independently hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, or —C₁-C₆ alkyl-O-aryl; and

represents an aryl.

An exemplary bis(3,4-ethylenedioxythienyl)arylenes according to structure (XIX) includes the compound wherein all Q¹ are O, both Q² are S, all R⁶ are hydrogen, and

is phenyl linked at the 1 and 4 positions. Another exemplary compound is where all Q¹ are 0, both Q² are S, all R⁶ are hydrogen, and

is thiophene linked at the 2 and 5 positions.

The class of compounds according to structure (XX):

wherein each occurrence of Q¹ is independently S or O; each occurrence of Q² is independently S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; Q⁴is C(R⁶)₂, S, O, or N—R⁷; and each occurrence of R⁶ is independently hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, or —C₁-C₆ alkyl-O-aryl. In one embodiment, each occurrence of Q¹ is O; each occurrence of Q² is S; each occurrence of R⁶ is hydrogen; and R⁷ is methyl.

The class of compounds according to structure (XXI):

wherein each occurrence of Q² is independently S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; Q⁴ is C(R⁶)₂, S, O, or N—R⁷; and each occurrence of R⁶ is independently hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, or —C₁-C₆ alkyl-O-aryl.

The class of compounds according to structure (XXII):

wherein each occurrence of Q² is independently S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; each occurrence of Q⁴ is C(R⁶)₂, S, O, or N—R⁷; and each occurrence of R⁶ is independently hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, or —C₁-C₆ alkyl-O-aryl.

The class of compounds according to structure (XXIII):

wherein Q² is S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; and each occurrence of Q¹ is independently S or O.

The class of compounds according to structure (XXIV):

wherein each occurrence of Q² is independently S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; and each occurrence of Q¹ is independently S or O.

The class of compounds according to structure (XXV):

wherein Q² is S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; each occurrence of Q¹ is independently S or O; and each occurrence of R⁶ is independently hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, —C₁-C₆ alkyl-aryl, —C₁-C₆ alkyl-O-aryl, or —C₁-C₆ alkyl-O-aryl. In one embodiment, one R⁶ is methyl and the other R⁶ is benzyl, —C₁-C₆ alkyl-O-phenyl, —C₁-C₆ alkyl-O-biphenyl, or —C₁-C₆ alkyl-biphenyl.

The class of compounds according to structure (XXVI):

wherein each occurrence of Q² is independently S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; each occurrence of Q¹ is independently S or O; and each occurrence of R⁶ is independently hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, or —C₁-C₆ alkyl-O-aryl. In one embodiment, one R⁶ is methyl and the other R⁶ is —C₁-C₆ alkyl-O-phenyl or —C₁-C₆ alkyl-O-biphenyl per geminal carbon center.

The class of compounds according to structure (XXVII):

wherein each occurrence of Q² is independently S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; each occurrence of Q¹ is independently S or O; each occurrence of R⁶ is independently hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, or —C₁-C₆ alkyl-O-aryl; and

represents an aryl. In one embodiment, one R⁶ is methyl and the other R⁶ is —C₁-C₆ alkyl-O-phenyl or —C₁-C₆ alkyl-O-biphenyl per geminal carbon center.

The class of compounds according to structure (XXVIII):

wherein each occurrence of Q² is independently S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; each occurrence of Q¹ is independently S or O; and each occurrence of R⁶ is independently hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, or —C₁-C₆ alkyl-O-aryl.

The class of compounds according to structure (XXIX):

wherein each occurrence of Q² is independently S, O, or N—R⁷ wherein R⁷ is hydrogen or C₁-C₆ alkyl; each occurrence of Q¹ is independently S or O; and each occurrence of R⁶ is independently hydrogen, C₁-C₁₂ alkyl, C₁-C₁₂ haloalkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ haloalkoxy, aryl, —C₁-C₆ alkyl-O—C₁-C₆ alkyl, or —C₁-C₆ alkyl-O-aryl.

In one embodiment, the copolymer comprises 1 to about 99 percent substituted PropOT monomer units, specifically about 20 to about 90 percent, more specifically about 30 to about 80 percent, and yet more specifically about 40 to about 70 percent substituted PropOT monomer units present in the copolymer based on the total units of the copolymer.

As used herein, “alkyl” includes straight chain, branched, and cyclic saturated aliphatic hydrocarbon groups, having the specified number of carbon atoms, generally from 1 to about 20 carbon atoms for the straight chain and generally from 3 to about 20 carbon atoms for the branched and cyclic. Examples of alkyl include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, 3-methylbutyl, t-butyl, n-pentyl, sec-pentyl, cyclopentyl, cyclohexyl, and octyl. Specific alkyl groups include lower alkyl groups, those alkyl groups having from 1 to about 8 carbon atoms, from 1 to about 6 carbon atoms, or from 1 to about 4 carbons atoms.

As used herein “haloalkyl” indicates straight chain, branched, and cyclic alkyl groups having the specified number of carbon atoms, substituted with 1 or more halogen atoms, generally up to the maximum allowable number of halogen atoms (“perhalogenated”, e.g. perfluorinated). Examples of haloalkyl include, but are not limited to, trifluoromethyl, difluoromethyl, 2-fluoroethyl, and penta-fluoroethyl.

As used herein, “alkoxy” includes an alkyl group as defined above with the indicated number of carbon atoms attached through an oxygen bridge (—O—). Examples of alkoxy include, but are not limited to, methoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, 2-butoxy, t-butoxy, n-pentoxy, 2-pentoxy, 3-pentoxy, isopentoxy, neopentoxy, n-hexoxy, 2-hexoxy, 3-hexoxy, and 3-methylpentoxy.

“Haloalkoxy” indicates a haloalkyl group as defined above attached through an oxygen bridge.

As used herein, the term “aryl” indicates aromatic groups containing only carbon in the aromatic ring or rings. Such aromatic groups may be further substituted with carbon or non-carbon atoms or groups. Typical aryl groups contain 1 or 2 separate, fused, or pendant rings and from 6 to about 12 ring atoms, without heteroatoms as ring members. Where indicated aryl groups may be substituted. Such substitution may include fusion to a 5 to 7-membered saturated cyclic group that optionally contains 1 or 2 heteroatoms independently chosen from N, O, and S, to form, for example, a 3,4-methylenedioxy-phenyl group. Aryl groups include, for example, phenyl, naphthyl, including 1-naphthyl and 2-naphthyl, anthracene, pentacene, fluorene, and bi-phenyl.

“Halo” or “halogen” as used herein refers to fluoro, chloro, bromo, or iodo.

Compounds are described using standard nomenclature. For example, any position not substituted by any indicated group is understood to have its valency filled by a bond as indicated, or a hydrogen atom. A dash (“-”) that is not between two letters or symbols is used to indicate a point of attachment for a substituent. For example, —CHO is attached through carbon of the carbonyl group.

Also contemplated herein are blends comprising two or more substituted PropOT polymers. Additionally, blends comprising at least one of the foregoing substituted PropOT polymers and an additional polymer are also contemplated. The additional polymer may be a conductive polymer, a nonconductive polymer, a thermoplastic or combinations comprising at least one of the foregoing.

In one method, a substituted PropOT monomer and an optional co-monomer is chemically oxidized in a liquid to form the substituted PropOT polymer. Suitable oxidants include the iron (III) salts of organic acids, inorganic acids containing organic residues, and inorganic acids, such as FeCl₃, Fe(ClO₄)₃. Oxidants such as H₂O₂, K₂Cr₂O₇, alkali or ammonium persulfates, alkali perborates, potassium permanganate, NOBF₄, or copper salts such as copper tetrafluoroborate may also be used. In addition, bromine, iodine, and oxygen may advantageously be used as oxidants. Persulfates and the iron (III) salts of organic acids and inorganic acids containing organic residues can be used because they are not corrosive. Examples of suitable iron (III) salts of organic acids are the Fe(III) salts of C₁-C₃₀ alkyl sulfonic acids, such as methane or dodecane sulfonic acid; aliphatic C₁-C₂₀ carboxylic acids, such as 2-ethylhexylcarboxylic acid; aliphatic C₁-C₂₀ perfluorocarboxylic acids, such as trifluoroacetic acid and perfluorooctanoic acid; aliphatic dicarboxylic acids, such as oxalic acid; and aromatic, optionally C₁-C₂₀ alkyl-substituted sulfonic acids, such as benzenesulfonic acid, p-toluene-sulfonic acid and dodecyl benzenesulfonic acid. Mixtures of the aforementioned Fe(III) salts of organic acids may also be used. Examples of iron (III) salts of inorganic acids containing organic residues are the iron (III) salts of sulfuric acid semiesters of C₁-C₂₀ alkanols, for example the Fe(III) salt of lauryl sulfate.

Suitable liquids for conducting the oxidative chemical reaction are those that do not adversely affect the reaction, and specifically are inert. Suitable liquids can further be selected on the basis of economics, environmental factors, and the like, and may be organic, aqueous, or a mixture thereof. Suitable organic liquids may be aliphatic alcohols such as methanol and ethanol; aliphatic ketones such as acetone and methyl ethyl ketone; aliphatic carboxylic esters such as ethyl acetate; aromatic hydrocarbons such as toluene and xylene; aliphatic hydrocarbons such as hexane; aliphatic nitriles such as acetonitrile; chlorinated hydrocarbons such as dichloromethane; aliphatic sulfoxides such as dimethyl sulfoxide; and the like, as well as mixtures comprising at least one of the foregoing organic liquids. Specifically aqueous liquids are used, that is, a liquid comprising water or water-miscible organic liquids such as lower alcohols, acetonitrile, tetrahydrofuran, dimethylacetamide, dimethylformamide, and the like.

Heat may not be necessary for the formation of the substituted PropOT polymer in the chemical oxidation process. However, it can be used to speed up the conversion to the conjugated polymers. Heat can be administered to the reaction medium either during its exposure to chemical oxidants or after the exposure. Typical reaction conditions include temperatures of about 0 to about 100° C. The oxidation is continued for a period of time until the desired conjugated polymer is prepared. The polymerization time may be a few minutes up to about 48 hours, and depends on a number of factors including the size of the reactor utilized, the reaction temperature, the oxidant utilized, and the like.

In one embodiment, a substituted PropOT monomer and an optional co-monomer is converted to a conjugated polymer by a chemical oxidant such as FeCl₃ or those previously discussed. When a chemical oxidant is used, the addition of a salt to the reaction solution can be used to get adequate oxidation. Suitable salts for this purpose include organic soluble salts, inorganic salts, ionic liquids, and polyelectrolytes such as polystyrene sulfonate, polyacrylic acid sodium salt, poly(meth)acrylic acid sodium salt, etc. Exemplary salts include tetra-alkyl ammonium, ammonium, lithium, or sodium cations with tetrafluoroborate, hexafluorophosphate, perchlorate, halides, toluenesulfonate and other aliphatic sulfonate salts, trifluoromethylsulfonate, bistrifluoromethanesulfonimide, sulfates, carbonates or persulfates.

An alternative method for preparing the substituted PropOT polymer is by electrochemical oxidation to convert a substituted PropOT monomer and an optional co-monomer to a conjugated polymer. Conventional electrolytic cells can be used for the reaction. In one embodiment, a three-electrode configuration (working electrode, counter electrode, and reference electrode) in operable communication with an electrolyte is used, comprising a working electrode, specifically a button working electrode selected from the group consisting of platinum, gold, vitreous carbon, and indium doped tin oxide working electrodes or non-button electrodes such as the ITO, and platinum flag, a platinum flag counter electrode, and an Ag/Ag⁺ non-aqueous reference electrode.

Suitable electrolytes include tetraalkylammonium salts, e.g., tetraethylammonium, tetrapropyl ammonium, tetrabutylammonium salts, as well as salts of cations such as lithium trifluoromethansulfonate. Suitable counter ions include but are not limited inorganic ions such as bistrifluoromethylsulfonimide, tosylate, perchlorate, tetrafluoroborate, hexafluorophosphate, and halides such as chloride, bromide, iodide, and organic anions such as tosylate, triflate, trifluoromethylsulfonimide, or polyanions, e.g., polystyrenesulfonate, the anionic form of acrylic acid. Solvents may be used to prepare an electrolyte solution, for example water, ethanol, methanol, acetonitrile, propylene carbonate, tetraglyme, methylene chloride, chloroform, and tetrahydrofuran. Specified solvents are water, acetonitrile, and propylene carbonate.

Other suitable electrolytes include ionic liquids such as butylmethylimidazolium hexafluorophosphate (BMIM PF₆) and butylmethylimidizolium tetrafluoroborate (BMIM BF₄).

Specified electrolytes include tetrabutylammonium perchlorate/acetonitrile, tetrabutylammonium tetrafluoroborate, tetrabutylammonium hexafluorophosphate/acetonitrile, lithium trifluoromethansulfonate/acetonitrile, and lithium triflate/acetonitrile. Exemplary concentrations of the electrolytes are about 0.05 to about 0.15, specifically about 0.1M.

A specified working electrode is a vitreous carbon electrode and the electrolyte is tetrabutylammonium hexafluorophosphate/acetonitrile. Another specified working electrode is a platinum button electrode and the electrolyte is tetrabutylammonium hexafluorophosphate/acetonitrile.

The substituted PropOT polymers disclosed herein provide for a transition from green to colorless, a result not achieved with previously known conjugated polymers.

The electrical conductivity of the films prepared from the polymers can be readily modified, if necessary, to meet the requirements of a desired application by doping with conventional acidic dopants (p-dopants) or basic dopants (n-dopants) known in the art. Suitable p-dopants include mineral acids such as HCl, HNO₃, H₂SO₄, H₃PO₄, HBr, and HI; organic sulfonic acids such as dodecyl benzene sulfonic acid, lauryl sulfonic acid, camphor sulfonic acid, organic acid dyes, methane sulfonic acid, and toluene sulfonic acid; polymeric sulfonic acids such as poly(styrene sulfonic acid) and copolymers of styrene sulfonic acids; carboxylic acids such as adipic acid, azelaic acid, and oxalic acid; and polycarboxylic acids such as poly(acrylic acid), poly(maleic acid), poly(methacrylic acid), and copolymers formed from acrylic acid, maleic acid, or methacrylic acid. Conventional mixed dopants comprising one or more of the foregoing, such as a mixture of a mineral acid and an organic acid, can also be used to impart the desired electroactive character to the films. Suitable basic dopants include, but are not limited to Na, K, Li, and Ca. Other suitable dopants include I₂, PF₆, SbF₆, and FeCl₃. In some instances the oxidant and the dopant may be the same.

Admixtures of the polymer with other electroactive materials such as laser dyes, other electroactive polymers, hole transport or electron transport materials, including electroactive organometallic compounds, are also contemplated herein. Such materials can be added to the polymer before or after formation of the solution or dispersion. Additives such as ethylene glycol, diethylene glycol, mannitol, propylene 1,3-glycol, butane 1,4-glycol, N-methylpyrrolidone, sorbitol, glycerol, propylene carbonate, and other appropriate high boiling organics may be added to dispersions of the polymeric compositions to improve conductivity.

Additional additives may also be used, and include conductive fillers such as particulate copper, silver, nickel, aluminum, carbon black (carbon nanotubes, buckminister fullerene), and the like; non-conductive fillers such as talc, mica, wollastonite, silica, clay, dyes, pigments (zeolites), and the like, to promote specific properties such as increased modulus, surface hardness, surface color and the like; antioxidants; UV stabilizers; viscosity modifiers; and surfactants such as acetylenic diols, surfactants typically being added to control stability, surface tension, and surface wettability.

The substituted PropOT polymers disclosed herein can be processed by conventional methods to provide uniform, thin films that possess utility in numerous applications. Films and materials comprising the above-described conjugated polymers can be utilized in a variety of applications, including antistatic coatings, electrically conductive coatings, electrochromics, photovoltaic devices, light emitting diodes for display applications, hole injection layers for light emitting diodes, near infrared light emitting diodes, transparent conductive coating for indium doped tin oxide replacement, flat panel displays, flexible displays, photoimageable circuits, printable circuits, thin film transistor devices, batteries, electrical switches, capacitor coatings, corrosion resistant coatings, electromagnetic shielding, sensors, biosensors, dimmable mirrors, type III supercapacitors, LED lighting, and the like, and specifically electrochromic windows, electrochromic films for reflective devices, and electrochromic displays. The electrical conductivity of the polymers can be readily modified, if necessary, to meet the requirements of any of the previously mentioned applications by doping the polymers with conventional dopants such as anions (for p-doped polymers) and cation dopants (for n-doped polymers) known in the art.

The following illustrative examples are provided to further describe how to make and use the polymers and are not intended to limit the scope of the claimed invention.

EXAMPLES Example 1 Preparation of a dimethyl substituted 3,4-propylenedioxythiophene (aDM-PropOT)

A three-neck round bottom flask is vacuum dried, fitted with a stir bar, thermometer, and drying tube and maintained under nitrogen. About 500 milliliters (ml) of anhydrous xylene is cannulated into the flask. Two ml of 3,4-dimethoxy thiophene 1 (DMOT) (0.0166 mol), 4.85 ml of 2,4-pentanediol 2 (0.0332), and 0.61 ml of catalyst dodecylbenzene sulfonic acid (DBSA) (0.0025 mol) are added to the flask sequentially with previously degassed disposable syringes through the rubber septa fitted on one of the necks of the flask. The molar proportion between DMOT:diol:DBSA is 1.00:2.00:0.15. The reaction is set to run for five days under stirring at a temperature of around 100° C. The reaction is monitored on a daily basis by gas chromatography-mass spectrometry (GC-MS). After five days, the reaction is cooled to ambient temperature and filtered to remove any solid particulates. The xylene is stripped using a rotary evaporator to result in a green oil. The oil is taken up in a small amount of chloroform and extracted with water three times using sodium chloride to break any emulsion. The chloroform is stripped leaving a green oil. The crude mixture is purified by column chromatography using 70:30 toluene:n-hexane as the eluting solvent. The first fractions contain the product 2,4-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine 3 (aDM-PropOT) and subsequent fractions contain DMOT 1 starting material. The aDM-PropOT 3 is isolated as a white solid that is dried under vacuum. The final product was confirmed by GC-MS and ¹H-NMR.

FIG. 1 illustrates the results of cyclic voltammetry of a 10 mM aDM-PropOT/100 mM tetrabutylammonium hexafluorophosphate (TBAPF₆) solution in acetonitrile at a scan rate of 100 mV/s at room temperature under normal atmospheric conditions.

Films were prepared having a thickness of about 500 nanometers (nm). The switching speed was about 160 milliseconds. Films are stable in the reduced state in open air for over twenty-four hours with full retention of the colored state. Films have been observed to be stable in the oxidized state in solute on for several minutes. FIG. 2 illustrates the scan rate study of a aDM-PropOT polymer film (15 polymerization scans yielded the film) at 50 mV/s-300 mV/s in 50 mV increments and 400-1000 mV/s in 100 mV increments in 0.1 M TBAPF₆/acetonitrile solution. The results indicate that the film is adhered to the electrode surface and that the redox activity for aDM-PropOT lies between 0V and 0.5 V. For thinner films, it is anticipated that there will be faster diffusion and less peak to peak separation upon increasing the scan rate (the polymer response will be faster).

FIG. 3 illustrates the spectroelectrochemistry of aDM-PropOT in 0.1 V potential steps in acetonitrile and 0.1 M TBAPF₆ on indium doped tin oxide (ITO) glass. The results indicate that in the neutral state that aDM-PropOT has an onset for the pi to pi* transition at ca. 650 nm (2 eV). Upon oxidation of the conjugated Poly(PropOT), there is a decrease in the intensity of the pi to pi* transition with an increase in absorbance at the longer wavelength end of the visible spectrum. Upon further oxidation, the absorbance at longer wavelength goes from increasing to decreasing upon further oxidation. This is beneficial for a chromic polymer in that it will lead to a polymer with less visibly noticeable color.

A preliminary investigation of the color coordinates for poly-aDM-PropOT is provided in Table 1 below.

TABLE 1 Voltage u′ v′ 1.1 0.2029 0.4701 1.0 0.2031 0.4700 0.9 0.2030 0.4694 0.8 0.2029 0.4692 0.7 0.2030 0.4695 0.6 0.2028 0.4699 0.5 0.2033 0.4699 0.4 0.2039 0.4694 0.3 0.2045 0.4660 0.2 0.2042 0.4626 0.1 0.2039 0.4611 0.0 0.2037 0.4608 −0.1 0.2038 0.4607 −0.2 0.2038 0.4611 −0.3 0.2039 0.4614 −0.4 0.2039 0.4616

Example 2 Preparation of additional substituted 3,4-propylenedioxythiophene (substituted PropOT)

Other substituted PropOT monomers (Table 2) can be prepared using the procedure outlined in Example 1.

TABLE 2 Name Abbreviation Structure 2,2,4,4-tetramethyl-3,4-dihydro- 2H-thieno[3,4-b][1,4]dioxepine aTM-ProDOT

2,4-dibenzyl-3,4-dihydro-2H- thieno[3,4-b][1,4]dioxepine aDB-ProDOT

2,2,4,4-tetrabenzyl-3,4-dihydro-2H- thieno[3,4-b][1,4]dioxepine aTB-ProDOT

The monomers of Table 2 are studied electrochemically using cyclic voltammetry to determine monomer oxidation potential, ease of polymerization, and polymer redox potentials. The resulting polymers are electrochemically deposited onto indium doped tin oxide coated glass from a monomer containing electrolyte solution. The electrochromic properties of the polymers are assessed using chronocoulometry in conjunction with spectrophotometry. The polymers are tested for switching speed, color using the 1976 CIE color coordinates, and memory effects. Switching speeds are determined by taking the polymer from the bleached state to the colored state at a thickness of the electrochromic polymer of 500 nm (optimal film thicknesses will be between 200 and 700 nm). Memory effects are tested by switching the polymer to the bleached state, and then removing power. While the power is off, the intensity a λ_(max) will be monitored as a function of time until there is 10% gain (10% of the optical contrast) in absorbance. The stability of the colored state will be evaluated by switching the polymer to the colored state, removing power, and monitoring λ_(max) as a function of time until there is 10% loss (10% of the optical contrast) in absorbance.

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising”, “having”, “including”, and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to”) unless otherwise noted. “Or” means and/or. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All ranges disclosed herein are inclusive and combinable.

The essential characteristics of the present invention are described completely in the foregoing disclosure. One skilled in the art can understand the invention and make various modifications without departing from the basic spirit of the invention, and without deviating from the scope and equivalents of the claims, which follow. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context. 

1. A substituted 3,4-propylenedioxythiophene according to the structure (I):

wherein each instance of R¹, R², R³, and R⁴ independently is hydrogen; optionally substituted C₃-C₂₀ alkyl, C₁-C₂₀ haloalkyl, aryl, C₁-C₂₀ alkoxy, C₁-C₂₀ haloalkoxy, aryloxy, —C₁-C₁₀ alkyl-O—C₁-C₁₀ alkyl, —C₁-C₁₀ alkyl-O-aryl, or —C₁-C₁₀ alkyl-aryl; or hydroxyl; with the proviso that at least one of a R¹ or a R² group is not hydrogen, and when R¹ or R² is an alkyl, at least two of the R¹ and R² groups are not hydrogen; wherein the C₃-C₂₀ alkyl, C₁-C₂₀ haloalkyl, aryl, C₁-C₂₀ alkoxy, C₁-C₂₀ haloalkoxy, aryloxy, —C₁-C₁₀ alkyl-O—C₁-C₁₀ alkyl, —C₁-C₁₀ alkyl-O-aryl, or —C₁-C₁₀ alkyl-aryl group each may be optionally substituted with one or more of C₁-C₂₀ alkyl; aryl; halogen; hydroxyl; —N—(R⁷)₂ wherein each R⁷ is independently hydrogen or C₁-C₆ alkyl; cyano; nitro; —COOH; —S(═O)C₀-C₁₀ alkyl; or —S(═O)₂C₀-C₁₀ alkyl.
 2. The substituted 3,4-propylenedioxythiophene of claim 1, wherein each instance of R¹ and R² independently is hydrogen; optionally substituted C₃-C₁₀ alkyl, C₁-C₁₀ haloalkyl, aryl, C₁-C₁₀ alkoxy, C₁-C₁₀ haloalkoxy, aryloxy, —C₁-C₅ alkyl-O—C₁-C₅ alkyl, —C₁-C₅ alkyl-O-aryl, or —C₁-C₅ alkyl-aryl; or hydroxyl; and R³ and R⁴ are both hydrogen.
 3. The substituted 3,4-propylenedioxythiophene of claim 1, wherein each instance of R¹ and R² independently is hydrogen; or optionally substituted C₃-C₅ alkyl, C₁-C₅ haloalkyl, aryl, C₁-C₅ alkoxy, C₁-C₅ haloalkoxy, aryloxy, —C₁-C₃ alkyl-O—C₁-C₃ alkyl, —C₁-C₃ alkyl-O-aryl, or —C₁-C₃ alkyl-aryl; or hydroxyl; and R³ and R⁴ are both hydrogen.
 4. The substituted 3,4-propylenedioxythiophene of claim 1, wherein each instance of R¹ and R² independently is hydrogen; or optionally substituted C₃-C₂₀ alkyl, C₁-C₂₀ haloalkyl, aryl, or —C₁-C₁₀ alkyl-aryl; and R³ and R⁴ are both hydrogen.
 5. The substituted 3,4-propylenedioxythiophene of claim 1, wherein each instance of R¹ and R² independently is hydrogen; or optionally substituted C₃-C₂₀ alkyl, C₁-C₂₀ haloalkyl, aryl, or —C₁-C₁₀ alkyl-aryl; and R³ and R⁴ are both hydrogen, with the proviso that at least two of the R¹ or R² groups are not hydrogen.
 6. The substituted 3,4-propylenedioxythiophene of claim 1, wherein each instance of R¹ and R² independently is hydrogen; or optionally substituted C₃-C₁₀ alkyl, or —C₁-C₁₀ alkyl-aryl; and R³ and R⁴ are both hydrogen, with the proviso that at least two of the R¹ or R² groups are not hydrogen.
 7. The substituted 3,4-propylenedioxythiophene of claim 1, wherein at least two of the R¹ and R² groups are not hydrogen while the remaining two are hydrogen.
 8. A method of preparing a substituted 3,4-propylenedioxythiophene according to the structure (I):

wherein each instance of R¹, R², R³, and R⁴ independently is hydrogen; optionally substituted C₃-C₂₀ alkyl, C₁-C₂₀ haloalkyl, aryl, C₁-C₂₀ alkoxy, C₁-C₂₀ haloalkoxy, aryloxy, —C₁-C₁₀ alkyl-O—C₁-C₁₀ alkyl, —C₁-C₁₀ alkyl-O-aryl, or —C₁-C₁₀ alkyl-aryl; or hydroxyl; wherein the C₁-C₂₀ alkyl, C₁-C₂₀ haloalkyl, aryl, C₁-C₂₀ alkoxy, C₁-C₂₀ haloalkoxy, aryloxy, —C₁-C₁₀ alkyl-O—C₁-C₁₀ alkyl, —C₁-C₁₀ alkyl-O-aryl, or —C₁-C₁₀ alkyl-aryl group each may be optionally substituted with one or more of C₁-C₂₀ alkyl; aryl; halogen; hydroxyl; —N—(R⁷)₂ wherein each R⁷ is independently hydrogen or C₁-C₆ alkyl; cyano; nitro; —COOH; —S(═O)C₀-C₁₀ alkyl; or —S(═O)₂C₀-C₁₀ alkyl; with the proviso that at least one of a R¹ or a R² group is not hydrogen, and when R¹ or R² is an alkyl, at least two of the R¹ and R² groups are not hydrogen, comprising reacting a 3,4-dialkoxythiophene according to the structure

wherein R⁵ is an alkyl group, with a substituted diol according to the structure

wherein R¹, R², R³, and R⁴ are as defined above, or their appropriately protected functional group equivalents.
 9. The method of claim 8, wherein each instance of R¹ and R² independently is hydrogen; optionally substituted C₃-C₁₀ alkyl, C₁-C₁₀ haloalkyl, aryl, C₁-C₁₀ alkoxy, C₁-C₁₀ haloalkoxy, aryloxy, —C₁-C₅ alkyl-O—C₁-C₅ alkyl, —C₁-C₅ alkyl-O— aryl, or —C₁-C₅ alkyl-aryl; or hydroxyl; and R³ and R⁴ are both hydrogen.
 10. The method of claim 8, wherein each instance of R¹ and R² independently is hydrogen; or optionally substituted C₃-C₅ alkyl, C₁-C₅ haloalkyl, aryl, C₁-C₅ alkoxy, C₁-C₅ haloalkoxy, aryloxy, —C₁-C₃ alkyl-O—C₁-C₃ alkyl, —C₁-C₃ alkyl-O-aryl, or —C₁-C₃ alkyl-aryl; or hydroxyl; and R³ and R⁴ are both hydrogen.
 11. The method of claim 8, wherein each instance of R¹ and R² independently is hydrogen; or optionally substituted C₃-C₂₀ alkyl, C₁-C₂₀ haloalkyl, aryl, or —C₁-C₁₀ alkyl-aryl; and R³ and R⁴ are both hydrogen.
 12. The method of claim 8, wherein each instance of R¹ and R² independently is hydrogen; or optionally substituted C₃-C₂₀ alkyl, C₁-C₂₀ haloalkyl, aryl, or —C₁-C₁₀ alkyl-aryl; and R³ and R⁴ are both hydrogen, with the proviso that at least two of the R¹ or R² groups are not hydrogen.
 13. The method of claim 8, wherein each instance of R¹ and R² independently is hydrogen; or optionally substituted C₃-C₁₀ alkyl, or —C₁-C₁₀ alkyl-aryl; and R³ and R⁴ are both hydrogen, with the proviso that at least two of the R¹ or R² groups are not hydrogen.
 14. The method of claim 8, wherein at least two of the R¹ and R² groups are not hydrogen while the remaining two are hydrogen.
 15. The method of claim 8, wherein R⁵ is C₁-C₄ alkyl. 